As the world aims to get more of its energy from renewable resources, hydropower has again become a big part of the conversation. Some have raised concerns over its usefulness and sustainability, while others say it’s crucial for the future of energy and the planet. Who’s right? Is hydropower practical?

The Main Hydropower Technologies

Hydropower facilities can produce power by harnessing the natural flow of a body of water or by controlling water with reservoirs. Three are three main types of hydro plants that use these two methods to varying extents.

Run-of-river plants rely on the natural flow of water to turn the turbines that generate electricity. These plants have lower construction costs than other types of hydro plants, but their effectiveness can vary significantly based on the time of year and volume of the water. These systems sometimes contain smaller, short-term storage ponds that enable more control over how much power the plant generates.

Reservoir hydro plants utilize dams to hold water in a reservoir for later use. This stored water can be used to generate power as demand requires, and some dams can hold years’ worth of power. Many reservoirs are created artificially, but natural lakes can sometimes be used as reservoirs as well. This type of plant offers more control but comes with higher costs and environmental impacts.

Hydropower can also be used for energy storage. A pumped storage plant or PSP consists of two reservoirs – an upper one and a lower one. PSPs use energy from the grid to move the water from the lower to the upper basin. When extra power is needed or electricity can be produced at a low cost, the water is let out of the upper reservoir and turns turbines to create electricity as it flows to the lower reservoir. This process results in a loss of 15 percent to 30 percent of the energy originally invested, so it’s useful for storage, not for electricity generation.

The Benefits of Hydropower

It’s a renewable energy source

One of the biggest advantages that hydropower offers is that it’s a renewable energy source. Since the natural process of the water cycle powers it, it will never run out although it could become temporarily unavailable in the case of extreme drought.

Since hydro doesn’t require a fuel, there’s no disruption of the environment caused by extracting fuels from the ground like there is with fossil fuels. And when those fossil fuels inevitably run out, we’ll need renewable sources of energy such as hydropower to power our lives and provide energy security.

It doesn’t produce emissions

In addition to being a renewable energy source, hydropower is also clean. It doesn’t require the burning of fuel like fossil fuels or create waste like nuclear does. It produces no emissions that contribute to pollution and global warming.

Using more emissions-free energy sources is especially important because of climate change. 25 percent of the world’s emissions come from electricity and heat production with an extra 10 percent coming from other energy industry activities such as the extraction of transportation of fuels. This means that lowering the emissions of the energy sector would significantly lower the world’s emissions totals.

Operating and maintenance costs are relatively low

Another advantage of using hydropower is that operating and maintenance costs are relatively low compared to other generation facilities. Dams and water turbines tend to last for a long time, and there’s no need to purchase fuel, which brings costs down considerably.

Hydropower is a renewable energy resource and doesn’t require the purchase of fuels from other states or nations. This means that those using hydropower don’t have to rely on other countries for their energy and have more power over their electricity generation.

This helps to keep costs relatively stable and helps ensure that electricity will be available no matter what goes on in the rest of the world. It also helps build the local economies where the power plants are located.

It provides reliable power, backup and storage

Hydro technologies have been in operation for year, so we know that they’re reliable. They offer more certainty about the amount of power that will be available than other renewable sources like wind and solar, which rely on the amount of natural resources available on a given day.

They’re also more reliable than fossil fuels in some ways as well, because they don’t rely on importing fuels that also have a finite availability. Hydro’s storage capabilities also provide a dependable source of backup energy in case energy demand surpasses supply. Hydropower storage can also help keep energy prices, because the stored energy can be saved until generation costs are low.

It creates recreation opportunities

As something of an added bonus, some of the reservoirs used for hydropower projects also provide a location for recreational activities such as fishing, swimming, boating and other water-related pastimes.

Many dams are located in picturesque natural places that are open for the public to enjoy, increasing opportunities for people to access nature. Many hydropower projects are actually required to allow people to use the reservoirs for recreation and nature activities.

The Drawbacks of Hydropower

It’s limited by geography

Hydropower projects are more limited by geography than other types of energy sources. In order to build a successful hydro plant, you need steady running water or a reservoir of water where you can build a dam. Not all locations are suited to this.

For more complex projects such as pumped storage plants, the requirements are even steeper. There needs to be high ground with an upper reservoir and a lower reservoir below that. Then, the technology must be installed to convert the location into a PSP.

Upfront costs can be high

Although operating and maintenance costs for hydropower projects are minimal and fuel costs are nonexistent, the upfront costs can be extensive. Designing and constructing a large dam is an expensive and complex undertaking that sometimes goes over budget. Siting a project can be complicated too.

The cost of a hydro project can vary depending on its location, scale and other factors, but hydro does have the potential to get expensive, at least at first.

It can damage the environment

Although hydro projects don’t require fuels that create emissions, they can impact the environment in other ways. In some cases, habitats may be destroyed to make way for a reservoir or dam.

Dams can also harm the water ecosystems in which they operate. Turbines and other equipment sometimes kill fish and other creatures, and changing the animals’ habitat can also be damaging.

Installing hydropower can also alter the quality of the water it’s located in. Water in reservoirs is more stagnant than water flowing through rivers, which facilitates the growth of algae that can overtake other plant and animal life.

Reservoir water is also generally colder and has less dissolved oxygen than water further downstream. When reservoir water is released downstream, it can harm the ecosystems it comes into contact with. If water isn’t released often enough, water downstream can even dry up, which is even more harmful.

It sometimes clashes with cultural beliefs

In certain cases, hydro projects are met with dispute due to cultural beliefs. In some areas, such as China and Nepal, religious and cultural beliefs say that mountains and rivers are sacred. Dams can also sometimes flood holy or culturally significant areas.

In some areas, people also believe that damaging holy mountains, rivers or other landmarks will cause bad things, such as wildfires or earthquakes to occur. Naturally, these people oppose the building of dams where they live.

It can displace people and livestock

In some of these same regions, building dams can displace people. To make room for the Three Gorges Dam in China, for instance, more than a million people were moved. Many of those people are still struggling with poverty.

Some of the people that have to relocate because of hydropower plant construction depend on the land to make a living as farmers. Livestock has little access to food and water, and after 30 hours livestock will face tissue loss. Relocation then becomes very impractical for farmers, who could suffer significant loss in their livelihood due to relocation.

Droughts affect availability

Although hydro plants are usually rather reliable, they are susceptible to changes to water supply than can occur because of droughts. Climate change may make this more of a problem.

Many scientists believe that climate change will, and is already, increasing the frequency and severity of droughts around the world. This could make hydro plants less reliable in the future. In other areas though, climate change could cause increased rainfall, which wouldn’t be a bad thing for hydropower unless the rain causes flooding.

Is Hydropower Practical?

Around two-thirds of the possible, economically viable hydropower resources in the world still haven’t been used. We have the opportunity to expand hydropower capacity, but should we?

Hydropower comes with both environmental benefits and disadvantages. It doesn’t create emissions like fossil fuel plants do but can damage the ecosystems they’re built in. Since global warming is such as pressing concern, the environmental benefits may outweigh the risks.

Hydropower plants must be sited, designed and constructed in environmentally responsible ways in order for them to make sense for the environment. At this point in time, droughts caused in part by global warming wouldn’t impact the effectiveness of hydro plants much. Perhaps, if hydro begins to take off, it can help stave off some of those droughts.

Economically, hydro projects would have to be considered on a case-by-case basis. In many cases, they make economic sense but they’d also have to be compared to other available energy resources.

There isn’t enough hydropower capacity to power all of our energy demand, so other energy resources will certainly have to be a part of the mix as well. In reality, the question of whether hydropower is practical is a solid sometimes. Each project needs to be examined individually, but in the right situations, hydropower could be a useful part of the electricity generation mix.

Author’s Bio:

Emily Folk is a freelance writer and blogger on conservation and sustainability. To see her latest posts, check out her blog, Conservation Folks, or follow her on Twitter, @emilysfolk!